APTT Ratio
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Department of Haematology
Notes
- The APTT Ratio is used to monitor patients on full dose Heparin.
- Low molecular weight Heparin (LMWH) has little effect on the APTT result, and monitoring is usually not necessary.
- Samples MUST be filled appropriately (there may be a frosted fill line). Overfilled, underfilled and haemolysed samples give erroneous results and will therefore not be tested.
- Test performed at CGH and GRH
Sample Requirements
3 ml or 3.5ml Trisodium Citrate tube
Turnaround Time
- Clinical emergency: 30 mins
- Other urgent sample: 60 mins
- Routine: within 2 hours
Reference range
Therapeutic Range (Heparinised Patients): Ratio 1.5 - 2.5
Interfering substances
Haemolysed samples should not be tested.
Time limit for add ons
Citrate sample must be received in lab within 6 hours. Time limit for add on = 6 hours.